Conventional gas turbine engines generally include a fan section and a core engine with the fan section having a larger diameter than that of the core engine. The fan section and the core engine are disposed about a longitudinal axis and are enclosed within an engine nacelle or case assembly.
Combustion gases are discharged from the core engine through a core exhaust nozzle while an annular fan flow, disposed radially outward of the primary airflow path, is discharged through an annular fan exhaust nozzle system defined between a fan nacelle and a core nacelle. A majority of thrust is produced by the pressurized fan air discharged through the fan exhaust nozzle, the remaining thrust being provided from the combustion gases discharged through the core exhaust nozzle.
Some gas turbine engines include variable area fan nozzle (VAFN) systems to selectively provide a smaller fan exit nozzle diameter to optimize operation during certain conditions. Although potentially beneficial, existing VAFN systems typically utilize relatively complex mechanisms that undesirably increase overall engine weight and decrease fuel efficiency, particularly considering that portions of the VAFN system may be mounted on portions of the case assemblies with different relative movements. For example, portions of the VAFN system may be positioned on or adjacent to transcowls of a thrust reverser actuation system. When deployed, the transcowls of a thrust reverser actuation system function to redirect the rearward thrust of the jet engine to a forward or semi-forward direction to decelerate the aircraft upon landing, thereby enhancing the braking of the aircraft. However, as noted above, the resulting relative movement of portions of the VAFN system may complicate design and operation.
Accordingly, it is desirable to provide improved VAFN systems that, for example, reduce complexity, weight, and cost in a turbofan engine. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.